Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to a dent removal device, and in particular
to a device for smoothing and shrinking dented plate by means of an electrode
fitted to a handle in the manner of a hammer, the electrode being connectable
to one pole of a voltage source, the other pole of which is connectable to
the plate to be worked, the electrodebeing surrounded by a coaxially disposed
cylindrical anti-dazzle device.
In dent removal devices of this type, such as those described in
* r example German Offenlegungschrift No. 2,362,103 filed December 14, 1973
by Erwin Schill, electrical joulean heat is used for brief local heating of
the parts of the plate to be worked. Generally this is done by firstly press-
ing out the indentations with a conventional dent removal tool and grinding
the uneven parts clean to improve their electrical conductivity. The plate
from which the dents are to be removed is then connected to one pole of a vol-
tage source, for example a welding transformer with an output of approximate-
ly 50 Volts, the other pole of which is connected to the dent removal device.
On touching the plate with the electrode the circuit is closed and the plate
is strongly heated for a split second during the contact. During the subse-
quent cooling period the plate is reshaped to conform to its initial state.
By repeatedly touching the plate with the electrode or by sliding the elec-
trode over the plate, the latter is gradually shaped into a smooth surface.
The essential advantage of this process over dent removal with
oxyacetylene welding equipment is that only brief local heating occurs. Thus
inner linings, cable~ines and the like are undamaged and do not need to be
removed during the repair of the plate. In addition, the plate~arts are
fairly free from stress after working, so that the stability of the repaired
plate part is maintained.
In the case of large areas or difficult plate repairs it is necessary
to include cooling pauses throughout because firstly it is necessary to wait
for the plate to reshape gradually during cooling to ascertain the respective
state of the re-formation, and secondly the neighbouring parts such as inner
linings gradually become hot. Furthermore, the quality of the dent removal
process falls with increa.s~ng temperature.
Internal works tests by reducing the working voltage and/or
current to delay the gradual heating of the plate have had only partial
success, since the process time increases more than proportionally. Thus
it is necessary to wipe the heated plate parts from time to time with for
example a wet cloth.
The present invention provides a device for smoothing and shrink-
ing a dented article, the arrangement comprising: an electrode for effect-
ing a heating of at least a portion of the article, said electrode including
an end face for contacting the article, said electrode and the dented
article being connectable with a voltage source; a cooling means adjacent
said electrode for cooling at least a portion of the article affected by
said electrode, said cooling means consisting of a means for selectively
impermanently taking up a cooling fluid; and a shield means mounted
coaxially with said electrode for shielding the electrode said shield
means including a cylindrical casing for accommodating said cooling means,
said cylindrical casing defining an annular space between said electrode
` and said casing with said cooling means being accommodated in said annular
space.
The present invention is based on the recognition that the
process may be carried out most conveniently when provision is made for
cooling the surrounding plate part simultaneously with the touching and the
local heating of an uneven area. By this means the working progress
attained is immediately fixed and smoothing can be continued without any
~ interruption in the work, since the operating personnel is able to ascertain
;~ the effect of the plate smoothing practically immediately after each touch-
ing or stroking with the electrode. Since the electrode is combined
directly with the cooling element, there is the further advantage that the
~ electrode material is heated to a lesser extent and is therefore subject
'~ 30 to less wear. At the same time a better surface quality of the worked
surface part is obtainedO
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The shield functions as an anti-dazzle device.
The cooling means is preferably an annular sponge held in an
annular space between the electrode and the anti-dazzle device, with its
outer end surface aligned with or projecting beyond the working surface
of the electrode. The dent removal devîce then needs only to be dipped into
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water at the beginning of the working, so that water is absorbed into the sponge.
~n touching or sliding over the plate, the vicinity of the area on tho plate
contacted by the electrode is we'ted with cooling water so that even with a
large working area there is no unduly great heating of the plate. It is
particularly advantageous if the sponge projects beyond the electrode working
surface so that the elastic resilience of the sponge allows only brief contact
between the electrode and the plate, while good cooling of the neighbouring
zones is ensured as the overlying sponge is to some extent squeezed and
therefore makes sufficient cooling water available.
,~ 10 It is also advantageous if the anti-dazzle device is of an elastic
material and its outer odge is approximately aligned with the electrode work-
- ing surface. ~y this means no damage can occur during the touching or sliding
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~; of the electrode, and the anti-dazzle device lies firmly on the plate thus
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~ preventing unnecessary water losses.
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In a further adv~ntageous construction of the cooling element, a
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~ compressed air line may open into the annular space between the electrode and
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` the anti-dazzle device. In this case particularly good cooling is obtained
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- if the compressed air is fed through several holes distributed about the
electrode in its immediate vicinity. The anti-dazzle device keeps the cooling
air in the region of the electrode, so that even with small air quan~ities
good cooling is obtained. Instead of compressed air, cooling water may altern-
atively be used.
Since the shape of plate indentations is very varied, it has proved
desirable for the electrode to be in the form of a replaceable cotter pin
locked in a cylindrical support which is slightly set back. The operation can
therefore be carried out with different electrode shapes and worn electrodes
can be easily replaced. The support for the cotter pin may be provided with
a flat end surface which can be used as an electrode if the cotter pin is
removed.
The invention will be further described, by way of exa~ple only, with
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reference to the accompanying dra~ings, in which:-
Figure 1 is a side view of a device according to the invention, inwhich the cooling element is in the form of a sponge; and
Figure 2 is a side view of a device according to the invention, iD
which the cooling element is further in the form of a compressed air or cooling
water line.
Throughout the drawings, like reference numerals indicate like parts.
~ In the dent removal device shown in Figure 1 an electrode holder 3
- is fixed to a handle 1 by means of a shank 2 in the manner of a hammer. The
handle 1, shank 2 and holder 3 are all provided with an insulating covering.
~: An electrode in the form of a replaceable, cylindrical copper cotter pin 4 is
locked in a central bore in the electrode holder 3.
- An anti-dazzle device 5 in the form of a casing is fixed to the
electrode holder 3 concentric with the electrode holder and with the electrode
4. The device 5 embraces a sponge 6 of annular shape, held in the interspace
between the electrode holder 3 and electrode 4 and the casing S. The sponge
is so dimensionet that its outer annular surface 6a projects beyond the
~- working surface 4a of the electrode and by lightly pressing against a plate
to be worked gives to such an extent that the electrode 4 comes into electrical
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contact with the plate. The casing 5 is of a rubber-like flexible material,
~-` so that by simply squeezing it the water delivery of the sponge 6 can be
` accelerated.
By arranging the sponge in the direct vicinity of the electrode and
its casing, the electrode is at the same time protected so that it cannot
come into unintentional contact with an exposed metal surface and cause short
circuiting. Moreover the user of the dent removal device is shielded from
the light flashes between the electrode and the plate which occur during
working.
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- If a larger electrode working surface is required, it is possible
to withdraw the cotter pin 4 and instead use the bottom end surface of the
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electrode hQlder as the electrode. In this case either the sponge 6 must be
pressed somewhat deeper into the casing 5 or a somewhat flatter sponge must
be used.
Electricity is supplied to the electrode holder 3 and the electrode
4 through a connecting line 7 which enters at the handle end of the dent removal
device~ The working voltage is about 42 to 52 Volts, and the current is about
60-9OAmps.-in the case of aluminum working about 120 Amps. Thus commercially
available welding transformers may be used for operating the dent removal de-
vice.
Figure 2, shows a dent removal device similar to that shown in
Figure 1, but further comprising a cooling line 8 which opens in the vicinity
of the electrode 4 and provides effective cooling by way of cooling air or
cooling water. The cooling line 8 is fed through a hose 9 which may be
coupled to the coDnecting line 7.
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The device according to the present invention offers the advantage
~, - that by combining the electrode with a cooling element extensive dent removal
work can be carried out on a piece without pauses for cooling, and that because
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~` of the cooling which automatically proceeds with the working the handling of
the device is considerably simplified as the user is able to immediately take
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into account the actual working progress attained.
The device according to the invention is also compact and may be-
produced at low cost.
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